The invention generally relates to methods for applying decorative designs to substrates using sublimation dyes.
With the widespread use of substrates in business and in the home, e.g., walls, countertops, furniture, etc., the need for suitably decorating substrates is obvious. It is generally known that substrates can be decorated by applying a decoration, for example, by printing a design on a transfer sheet, bringing the decorated transfer sheet into contact with a substrate, and by the application of heat and pressure, transferring the decoration from the transfer sheet to the surface of the substrate.
Decorative surface papers generally weigh between 60 and 130 grams per square meter. These papers are saturated with reactive resins which are partially cured at the point of manufacture. Final curing is done at the time of hot press lamination when the resin forms a hard crosslinked thermoset material. The paper formation is similar to the sheet used for high pressure laminates. These products are self-bonding, i.e., the resin in the paper flows into the surface of the board during lamination to create a permanent bond.
Two different resin systems may be used to impregnate saturated paper for lamination. In accordance with the first system, melamine is introduced into the paper during an impregnation operation. After the paper is impregnated, it is partially cured using curing ovens. The melamine resin is fully cured at 300-400 psi and 300xc2x0-400xc2x0 F. during hot press lamination. This paper has a definite shelf life that varies with temperature and humidity.
The second resin system employs a polyester resin which is similarly introduced into the paper during an impregnation operation. The paper is heavily impregnated with polyester resin in a dip tank and then partially dried in a drying oven (260xc2x0-270xc2x0 F.). The polyester resin is fully cured at 140 psi and 300xc2x0-370xc2x0 F. during hot press lamination. The dried paper has a definite shelf life that varies with temperature and humidity.
The typical construction of a continuous laminate is a melamine-impregnated, alpha cellulose overlay plus a paper superimposed over one or more phenolic or resin impregnated papers. The laminate is formed on a continuous double band press at temperatures between 275xc2x0-300xc2x0 F. and pressure between 125-175 psi. The thickness of the laminate, which is normally in the {fraction (1/32)}xe2x80x3 range, is ultimately determined by the layers of papers and the resulting amount of resin absorbed. When the sheet is pressed, a steel caul plate is used to create a surface finish ranging from high gloss smooth to fully textured. Continuous laminates can be rolled, but only into larger diameter rolls. The storage of such large diameter rolls is problematic which presents potential inventory related difficulties.
Therefore, there remains a need for a cost-efficient method for the manufacture of decorative thermofused continuous laminates which store easily and cheaply as compact rolls and which can be easily bound to substrates with an adhesive.
Accordingly, the invention provides a practical cost-efficient method for the manufacture of decorative substrates that are advantageously distinguished by an improvement in properties including dyeability, weathering resistance and cleanability. In addition, the invention provides an advantageous method for the manufacture of decorative thermofused continuous laminates which store easily and cheaply as compact rolls and which can be easily bound to substrates with an adhesive. Other advantages of the invention will appear from the following description of the preferred embodiment.
The present invention relates to a method for transferring a decorative sublimation dye design formed on a transfer sheet to a continuous laminate. In accordance with the method defining the invention, a sheet of cellulose web material impregnated with a thermosetting resin such as, for example, polyester, is applied to a surface of a backer sheet to form a pre-laminate. The polyester impregnated cellulose web material may also include an aluminum oxide. An example of a cellulose web material that may be used in the present invention is paper. Latex is an example of a backer sheet material that may be used in the present invention. A release sheet is then applied to the exposed surface of the sheet of cellulose web material. Polyethelene film with a thickness of about 2 mil is an example of a suitable release sheet material that may be used in the present invention. The transfer sheet bearing the decorative sublimation dye design is applied to the exposed surface of the release sheet.
Heat and pressure are applied to the pre-laminate layered with the release and transfer sheets. The application of heat and pressure causes the cellulose web material to seep into the pores of the backer sheet to form a thermofused continuous laminate, and causes the design on the transfer sheet to penetrate the thermofused continuous laminate through a sublimation process. The thermofusing and sublimation processes occur substantially simultaneously at a temperature ranging from about 325xc2x0 F. to about 400xc2x0 F. and a pressure ranging from about 50 psi to about 150 psi. The release and transfer sheets are then separated from the thermofused continuous laminate showing the transferred design.
In another embodiment of the invention, a protective coating such as, for example, a UV cured polyester topcoat, is applied over the surface of the thermofused continuous laminate showing the transferred design. The thus prepared thermofused continuous laminate showing the transferred design is then available for bonding to a substrate such as, for example, plexiglass, glass, PVC, acrylics, cement, wood, engineered wood substrates and plastics with an adhesive.
One of the advantages of the present invention is that the decorative thermofused continuous laminates prepared in accordance with the invention can be used to decorate virtually any substrate by bonding the continuous laminate to the substrate with an appropriate adhesive. Hence, as opposed to the prior art requirement of maintaining an inventory of many different polyester impregnated thermofused substrates of limited shelf lives for the purpose of decorating them with sublimation dyes at a future date, the present invention allows one to simply inventory pre-decorated thermofused continuous laminates which may be stored easily as compact rolls, which have indefinite shelf lives and which may easily be bonded with an adhesive to any one of many different substrates at a future date. Moreover, decoration with sublimation dyes need not be limited to substrates that will not melt or distort under the high temperatures required for the sublimation process since. Advantageously, in accordance with the invention, the substrate need not be present during the laminating process but rather may be bonded to the thermofused continuous laminate after the laminating process has already taken place.